In a paper of 't Hooft about the rôle of magnetic monopoles for a model of quark confinement, I don't understand the following sentence (end at paragraph 14)
[...] in order for monopoles to produce a magnetic Higgs mechanism they must become very light.
What is to background for this statement? Why do they need to be (very) light?
I do think that it is related to the ype of superconductor you need to have a confining effect. For field generated by the pairs of quarks to be confined, you need flux tubes to be allowed inside condensed monopole-medium, i.e. you need a type II superconductor.
From Wikipedia I read that the type of SC is determined by:
The ratio of the London penetration depth λ to the superconducting coherence length ξ determines whether a superconductor is type-I or type-II. Type-I superconductors are those with 0 < λ/ξ < 1/√2, and type-II superconductors are those with λ/ξ > 1/√2
Although it is not explicitly shown in the article I suppose that the attenuation length must be inversely proportional to the mass of the monopoles of the theory...
Is this right? (If this is the case could someone give me a reference?)
G. t' Hooft, The Topological Mechanism for Permanent Quark Confinement in a Non-Abelian Gauge Theory. (Link to the article )